In the prior art, there have been many types of drill platforms that are erected at the site of drilling and use a large number of drill strings (tubes) that are strung one after another to drill down deep into the soil or rock. This approach requires a substantial amount of mass and volume as well as power to perform deep drilling with a long string of drill tubes into the ground. In all cases where conventional drill rigs are used, a flushing mechanism is also required for the purpose of removing cuttings from the hole as well as for cooling and lubricating the drill bit far down in the hole.
The disadvantages of the prior art are many. The conventional drill platform requires a great deal of mass and packaging volume to accomplish its task. Typically, there is a degree of assembly or deployment involved as well as manpower to perform the drilling operations that adds to the overall complexity and therefore risk. They also must employ a flushing system, whether it is air or a liquid of some kind, for the removal of cuttings from the hole as well as for drill bit lubrication and cooling. This type of massive, high power, complex machinery and associated flushing system would be totally unacceptable for use as probes that have to be flown and landed on any extraterrestrial bodies. Moreover, the massive amounts of material that would have to be left behind would be a waste of resources and might contaminate the alien surroundings, thus compromising scientific objectives.
There have been recent proposals to use drilling devices that have autonomous mobility underground using the “inch-worm” type of locomotion in which a forward section drills forward into the ground while a rearward section contracts to the position of the forward section, then the rearward section plants itself in place while the forward section extends itself and drills further ahead. However, in the proposed devices cuttings from the unit are passed back up to the ground station through a vacuum-powered tether or umbilical tube. The tether is also used to supply electric power down to the unit. However, tether management for a subsurface probe that travels to depths below a kilometer may be an insurmountable engineering problem, especially in a planetary exploration setting.